The shadowy staff padding has gone on for years in some schools, with the encouragement of principals and the department turning a blind eye.

“The DOE knows,” one PTA insider said. “It’s just something that we kind of keep quiet, and the DOE looks the other way.”

Among the generous spenders:

* At PS 6 on the Upper East Side, the PTA raised $831,000 last year and hired 16 assistant teachers for grades K through 3. It also pays for extras such as ballroom dancing, computer labs and air conditioning.

* At PS 87 on the Upper West Side, the PTA reported $1.2 million in revenue, including $883,300 in fees it collected for an award-winning after-school program. It hired six kindergarten assistant teachers and pays for nature trips, arts, furniture and staff training.

* At PS 158 on the Upper East Side, the PTA hauled in $886,554 last year. It hires assistant teachers, a full-time chess instructor and recess coaches. It pays for circus-arts and dance programs.

One Manhattan principal was uneasy discussing the PTA-hired aides.

“I don’t want to ruin a great thing we have for the school. I’m not sure how legal it is,” the principal told The Post.

At PS 8 in Brooklyn Heights, Principal Seth Phillips has urged the PTA to double what it raises so it can hire more assistants to help teachers with large class sizes, said PTA President Lisa Edstrom.

“We set up a payroll. We hire the teacher assistants, and they answer to us as their employers, but their instructions come from the teachers they work with,” she said.

Chancellor’s regulations forbid parent groups to fund “core instructional staff,” including the main classroom teacher, or math, science and English teachers. Parents may pay for “supplemental” staff such as music teachers.

DOE spokesman David Cantor said supplemental staff could include assistant teachers. But to fund any personnel working during school hours, PTAs must give the money to the school, which would pass it to a central office that issues the paychecks.

Cantor said he has “no doubt” some schools break the rules, but added, “That’s something we want to know, and we will rectify it.”

Last academic year, 26 schools gave a total of $1.1 million in PTA money through the proper channels to hire staff, according to a DOE list. The department requires all employees who work with kids to go through a background check.

“The rules are in place for a reason – to protect the kids and the school,” Cantor said.

Principals and PTA leaders who hire on the side say that they jointly interview assistant teachers, and that many are graduate education students working toward certification. Some assistants are licensed substitutes.

The PTAs pay the assistant teachers slightly less than DOE hires – in some cases $12 to $15 an hour with no benefits.

If the schools followed the rules and went through the department, they would have to pay wages and benefits for “paraprofessionals.”

Corey Feldman, 26, earns $12 an hour for a 34-hour workweek as an assistant teacher at PS 6. Feldman is going for a master’s degree in education at Brooklyn College and found the job on Craigslist. He has no insurance, but said the job counts as student teaching, which is usually unpaid.

“Not many schools have assistant teachers,” he said.

The richest PTAs not only hire, but shower their schools with extras.

They pay regular teachers overtime to work at recess or after hours. They contract with vendors for programs in art, theater, dance and music.

PTA leaders are proud of their efforts, but sympathetic toward schools where parents can’t bestow the same largesse.

“The sad truth is, the more affluent the neighborhood, the better the school is,” said Amanda Wolf, PTA co-president at PS 6.

In most cases, PTAs ask each family to give gifts in suggested amounts ranging from $500 to $1,800.

They also hold fund-raisers, from bake sales to auctions that sell anything from Broadway tickets to Botox.

Cantor of the DOE said: “Schools can always use more resources, especially in a time of reduced budgets. I wish that all schools had it.”

Parents consider their donations a bargain.

Upper East Sider Susan Friedland, whose daughter goes to Lower Lab School, said the $950 suggested donation is “more than acceptable. I don’t think $30,000 for a private school could buy what we get here.”

It shares its Third Avenue building with PS 198, where up to 80 percent of families received public assistance in 2006-07.

With class sizes at PS 198 as high as 30 students in grades 3 to 5, assistant teachers would make a huge difference, said Principal Sharon Jeffrey Roebuck. But her PTA doesn’t raise enough to hire any.